1. Field of the Invention
The present invention relates to a method and an apparatus for adjusting a cooking temperature in a microwave oven, and more particularly, the present invention relates to a method and an apparatus for adjusting a cooking temperature of a microwave oven, which can compensate for temperature differences caused when detecting the temperature of food on a rotating turntable in the microwave oven.
2. Description of Related Art
Generally, a microwave oven is widely used. Accordingly, a higher level of functionality is in demand because it is crucial to ensure reliability in end products. With the availability of various types of pre-cooked and quick cooking food, a microwave oven serves as a cooking utensil which can quickly and easily perform cooking operations in an office or a convenience store, as well as home.
When a microwave oven performs cooking operations, a specific sensor means is used to control a heating operation. For example, when a microwave oven has an infrared sensor, food temperature is detected by the infrared sensor, and heating time is controlled based on the detected temperature. Also, when a microwave oven has a humidity sensor, humidity is detected by the humidity in the oven sensor, and heating time is controlled based on the detected humidity.
FIGS. 1 and 2, show front views of a conventional microwave oven, and FIG. 3 is a block diagram illustrating a discriminating mechanism in a conventional microwave oven.
A sensor hole 4 is formed at an upper portion of one of side walls of cooking compartment 1. An infrared sensor 5 is mounted in the microwave oven to remotely detect a temperature of a food load 7 located in the cooking compartment 1 through the sensor hole 4. A signal from the infrared sensor 5 is inputted to discriminating mechanism 6. The discriminating mechanism 6 controls a heating operation of heating device 3, which generates microwaves and controls operation of other oven components, based on the signal from the infrared sensor 5.
A turntable driving motor 8 is mounted below the cooking compartment 1, and is driven under a control of the discriminating mechanism 6. A turntable 2 is fixed to a shaft of the turntable driving motor 8 centrally disposed in the cooking compartment 1. The load 7 including food to be cooked is put on the turntable 2.
According to the conventional microwave oven constructed as mentioned above, the discriminating mechanism 6 controls the heating device 3 and the turntable driving motor 8 based on the signal detected by the infrared sensor 5. Therefore, the food load 7 positioned in the cooking compartment 1 is heated by the microwaves generated by the heating device 3. The turntable 2 rotates while the heating device 3 is operates, to distribute microwave energy to the food load 7.
Referring to FIG. 3, the discriminating mechanism 6 includes a key input section 6a for inputting an intended cooking temperature, cooking time, and a cooking mode, a preset temperature memory 6b for storing the intended cooking temperature inputted through the key input section 6a (or a preset temperature), a current temperature memory 6c for temporarily storing a current temperature detected by the infrared sensor 5, a display section 6d for displaying (through a liquid crystal display) a simple message including the preset temperature, the current temperature, the cooking time, etc., and an output control section 6e for controlling an output by comparing the current temperature with the preset temperature.
The discriminating mechanism 6 discriminates the current temperature of the load 7 based on the signal detected by the infrared sensor 5. The discriminating mechanism 6 performs cooking operation by actuating the heating device 3 until the detected current temperature reaches the preset temperature.
While the FIG. 1 shows the load 7 centrally positioned on the turntable 2, FIG. 2 shows the load 7 offset from a center of the turntable 2.
Hereinafter, the cooking operation of a conventional microwave oven, constructed as mentioned above, will be described in detail.
FIG. 4, is a flow chart for explaining a cooking operation of the conventional microwave oven.
A user puts the load 7 onto the turntable 2 in the cooking compartment 1, inputs the cooking temperature through the key input section 6a to store the cooking temperature as the preset temperature into the preset temperature memory 6b, and presses a cooking start key. At this time, the output control section 6e actuates the heating device 3 to heat the load 7. The output control section 6e is maintained in a stand-by state for about 5 seconds after heating of the load 7 begins, without sensing the temperature of the load 7 with the infrared sensor 5, to prevent an error from being induced on the detected temperature due to oscillating noise, etc. (step 110).
The temperature of the load 7 put in the cooking compartment 1 rises as the heating operation of the heating means 3 proceeds. The output control section 6e begins to receive the temperature signal detected by the infrared sensor 5 after a predetermined time (for example, about 5 seconds) elapses since the start of the heating operation (step 120).
The output control section 6e compares the current temperature of the load 7, which is detected by the infrared sensor 5, with the preset temperature (step 130). If the current temperature is lower than the preset temperature, the output control section 6e continues to actuate the heating device 3 thereby to heat the load 7. If the current temperature reaches the preset temperature, the output control section 6e stops the operation of the heating device 3 to complete the cooking operation (step 140).
In other words, in the cooking operation of the conventional microwave oven of the prior art, the current temperature of the load 7, which is detected by the infrared sensor 5, is compared with the preset temperature. If the current temperature is lower than the preset temperature, the heating device 3 continues to heat the load 7. If the current temperature reaches the preset temperature, the operation of the heating device 3 is stopped to complete the cooking operation.
However, in the conventional microwave, even when the same food is cooked under the same cooking conditions, actual food temperatures may be different at different times when the cooking operations is completed. This is because the current temperature detected by the infrared sensor 5 varies depending on rotation of the turntable 2.
That is, as shown in FIG. 1, when the load 7 is centrally positioned on the turntable 2, when the current temperature of the load 7 reaches the preset temperature, cooking is completed. The current temperature of the load 7 depends on the rotating cycle of the turntable 2 with the load 7 is centrally positioned on the turntable 2.
However, with the load 7 is offset from the center of the turntable 2, the load 7 the may emit more heat or less heat relative to infrared sensors when compared to the state as shown in FIG. 1.
As a result, the load 7 can be more highly heated for turntable rotation cycle time (generally, between about 10 through 24 seconds) (denoted as "dT" in FIG. 5) of the turntable 2 from a time when an actual temperature of the load 7 reaches the preset temperature. This is because the current temperature detected by the infrared sensor 5 varies in synchronization with the rotation cycle of the turntable 2.
Generally, a highest temperature among temperatures detected by the infrared sensor 5 is close to the actual temperature of the load 7. However, even when the actual temperature of the load 7 reaches the preset temperature at an initial stage of the rotating cycle of the turntable 2, the heating operation may continue until a corresponding rotating cycle of the turntable is completely ended.
This is because the discriminating mechanism 6 decides whether the current temperature reaches the preset temperature only when a highest temperature is detected during the corresponding rotating cycle of the turntable 2. Accordingly, the discriminating mechanism 6 continuously detects the temperature of the load 7 until the corresponding rotating cycle of the turntable 2 completely ends. For this reason, the heating operation controlled by the discriminating mechanism 6 is continuously performed until the corresponding rotating cycle of the turntable 2 is completely ended. Therefore, a time when the discriminating mechanism 6 decides that the current temperature reaches the preset temperature, may vary within the rotation cycle time (of about 10 through 24 seconds) from the time when the actual temperature actually reaches the preset temperature.
In particular, if the food load 7 is small, the temperature of the food can be raised to a great extent for the rotating cycle of the turntable 2. For this reason, the temperature of the food after cooking, may vary by a great extent from the preset temperature.